1. Field of the Invention
The present invention relates to a safety device, and in particular to a device enabling personnel to perform maintenance or inspection procedures on large items, such as the wing or tail sections of an aircraft, the sides of storage tanks, ships, submarines and other large structures.
2. Description of the Prior Art
Because of the large open spans required in hanger buildings suitable for large aircraft, it is impractical to install fixed safety lines in these structures since the sag that would be induced in a line by the weight of a person falling and being arrested by the line could cause that person to strike a lower obstruction before their fall was arrested or to slide in an uncontrolled manner onto a protruding platform or lower part of an aircraft.
According to a first aspect of the present invention there is provided a safety device comprising an anchor which can be secured to a surface without damaging the surface, the anchor incorporating attachment means for attachment to a safety line.
It is thus possible to provide a safety device which can be positioned on a structure in the vicinity where a person is working thereby ensuring that the person is attached to the safety device by a relatively short safety line.
Preferably the anchor attaches to the surface by means of suction. Alternatively, other forms of attachment may be used, such a magnetic attraction generated by an electromagnet or a permanent magnet.
Preferably the anchor comprises a rigid element having a sealing element extending from a first side thereof. The rigid element may be formed as a plate. The sealing element may be formed as a seal extending around the periphery of the rigid element.
The plate may, for example, be circular or rectangular. A substantially square plate having chamfered corners has been found to be particularly useful in an embodiment of the present invention.
The plate is preferably made of a lightweight and strong material, such as aluminium or an aluminium alloy, as this enables a physically strong anchor to be formed which is still sufficiently light to be manually handled with ease. In an embodiment of the present invention, the plate is substantially 450 mmxc3x97450 mm with a thickness of approximately 10 mm. The plate may be planar or it may be curved in order to accommodate the curvature of a structure such as an aircraft fuselage. A planar plate may be used as an anchor on a curved fuselage provided that the radius of curvature is not too small. Similarly, a curved plate may be attachable to both a curved surface and a plane surface provided that the radius of curvature induced in the plate is not too small.
Advantageously, the seal is profiled to have a plurality of sealing lips. The provision of a plurality of lips provides enhanced integrity against gas leakage through the seal. In a preferred embodiment, the seal comprises a primary sealing lip and a secondary, tertiary, and quaternary lips which act as backup seals.
Preferably, the seal is made of a rubber or rubber-like material. Nitrile rubber is especially preferred as it has excellent resistance to chemical attack from items such as fuel, skydrol or mineral based oils used in aircraft systems.
The plate and seal cooperate to define a working volume of the anchor. This working volume becomes a sealed working chamber when the anchor is attached to the surface.
Preferably, each anchor carries its own control valves. One or more valves may be attached to the rear surface of the plate. Advantageously, the valves are positioned in a protective enclosure so that the valves cannot be inadvertently operated, for example, by someone accidentally tripping over the anchor. The valve or valves are operable to selectively to connect the working chamber to a vacuum source, or to vent the working chamber to the atmosphere. Advantageously the valve or valves may enable the working chamber to be isolated.
Preferably, each anchor comprises at least one coupling to enable it to be attached to or uncoupled from a vacuum supply line. Advantageously the couplings are quick release couplings. Preferably, each anchor carries two or more couplings in gas flow communication with one another such that a plurality of anchors may be connected together in series. Preferably, each coupling includes a self-sealing valve such that air is not admitted into the anchor in the event of accidental disconnection of a coupling.
Preferably, each anchor includes a vacuum reservoir. The reservoir can be selectively coupled to the working chamber of the anchor in order to reduce the gas pressure within the working chamber even when the vacuum supply to the anchor has been interrupted or removed.
Advantageously, the or each anchor carries a centrally mounted rotatable arm on its rear surface. The arm has an aperture formed therein for accepting a karabiner or other clip by which a connection can be made between the anchor and a safety line. The arm is rotatable thereby enabling a person to work safely within a predetermined radius of the anchor.
Alternatively, two anchors may be provided with a safety line that runs between them. A further safety line is then connected in sliding arrangement to the line secured between the two anchors. Such an arrangement enables a greater working area to be covered than is possible using a single anchor alone.
Preferably, one or more anchors are provided in combination with a substantially rigid track. Use of a rigid track reduces the shearing loads applied to the or each anchor when restraining a falling body. In a preferred embodiment, anchors are provided at opposing ends of track sections. Each track section is approximately 2.5 metres long and is provided with male and female ends, or another coupling arrangement, such that adjacent sections of track can be secured together. It is thus possible to form continuous track sections to any desired length. Advantageously, a carriage engages the track and is longitudinally moveable with respect thereto in order to give maintenance personnel easy access to a large area of structure whilst still providing excellent fall restraint.
Advantageously, a trolley is provided for storing the anchors or the track sections having anchors attached thereto. The trolley may also include a vacuum source together with flexible piping. The vacuum source may be driven from an electrical supply, a compressed air supply, a hydraulic supply or an internal combustion engine. Advantageously, the vacuum source also includes a safety system which will give an audible and/or visible warning in the event of failure of the vacuum system and/or the vacuum pump power source.
According to a second aspect of the present invention, there is provided a fall arrest system comprising a plurality of track elements connectable together to form an elongate track and a carriage moveable along the track, the carriage having a connector for connection to a safety line, in which each track section has at least one vacuum anchor so that the track can be secured to the surface of a structure without substantially damaging the surface.
According to a third aspect of the present invention, there is provided a method of fall restraint comprising placing at least one vacuum anchor against a suitable surface, operating the anchor so as to secure it to the surface without damaging the surface and attaching a safety line to the anchor.